Is there anyway I can pass width height as percentage when creating SVGGraphics2D? I couldn't find percentage in SVGUnits neither.Or is there anyway to change width & height later after elements are placed? I'm getting the elements from the database and it would be great if I could define width & height after finding out left most & right most coordinates of my elements.

I have to admit I didn't realise that % is a valid unit in the SVG width and height attributes so I need to spend a little more time looking at this. For sure you can't specify percentage using the current version of SVG, but maybe the viewBox attribute will do what you need.